Due to tolerances allowed during manufacturing, the thickness of different floorboards may slightly differ. As a consequence, different portions of a mechanical locking system may be arranged at different heights of the floorboards. For example, the distance from the sub floor on which the floorboards are arranged to a tongue arranged on a first floorboard may be different from the distance from the sub floor to a tongue groove of a second floorboard, into which the tongue is to be inserted for locking in a vertical direction, which is shown in FIG. 1. This may result in difficulties when joining the floorboards, since the floorboards may not enter into a locking position. However, such differences in thickness of the floorboards usually does not results in problems when locking the floorboards together when the floorboards are arranged on a foam provided on the sub-floor. Such a foam is usually compressible. The compressible foam allows a thicker floorboard to be pressed towards the sub-floor such that the tongue groove on the thicker floorboard is positioned at the same height as the tongue of an adjacent floorboard.
Such an underlying foam is conventionally used when installing laminate flooring, engineered wood floorings, etc. When installing floors made of plastics, such as vinyl floorings, for example LVT (Luxury Vinyl Tiles), such a foam is not conventionally used.
As a result, the differences in thickness between different floorboards may result in difficulties when locking the floorboards together, especially when joining the floorboards by a so called fold down technique. The fold down technique involves assembling the floorboards by a vertical downward movement of one edge of one of the floorboards. As described above, floorboards having different thickness may result in the tongue groove of one floorboard being positioned at a different height than the tongue of the adjacent floorboard, resulting in difficulties when joining the floorboards, because the floorboards may not enter into a locking position.